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This comet appears to be fading. I imaged it this morning (April 11.14) and I get a total magnitude of 9.6 and coma diameter of 2.3′ using comphot on the green pixels vs Gaia DR3. My last measurement was on April 9.14 when I got mag 8.6 and 3.0′. Some of this will be the brighter sky due to the Moon but the comet is also fainter in my 9 arcsec aperture photometry.
The attached plot shows 9 arcsec photometry from myself, Denis Buczynski and Peter Carson. Shortly after discovery the magnitude rose rapidly but it is now fading. Total magnitudes are shown on the COBS lightcurve here:
There is a huge amount of scatter on these from different observers. To see a trend you need to look at the results from a single observer using the same equipment and method. Mine are here:
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My image taken on the morning of 20250410 from Tarbatness Highland Scotland.
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The press (or at least the Guardian) has caught on to this. They are asking for readers’ images of 2025 F2: https://www.theguardian.com/science/2025/apr/10/share-your-pictures-of-the-comet-c2025-f2-swan
Time was when it was hard to get the national press to cover an eclipse, but now its bizarre which astronomical happenings (or non-events) they will run with: a mag. 9 comet hard to see from the UK in morning twilight. I suppose they can’t claim a ‘rare planetary alignment’ or ‘supermoon’ every day.
This is my Seestar50 image. 14 minutes of 10 second exposures stacked in Astro Pixel Processor. AltAz mode, on 12th April.
Some posts from today (17 April) on the comet groups/io mailing suggest that the comet seems to be breaking up and now hardly visible.
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Yes, it does look very much as if this comet has expired. There are not many recent magnitudes on COBS but it seems to have stalled at around 8th magnitude and then faded. I haven’t managed to observe it for a few days due to the weather.
I’m not able to get onto the comet with my main telescope until it clears my house roof, by which time the sky is very bright, but here is an image from this morning (April 18.17). There is apparently no distinct photocentre any more.
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Peter Carson managed to image C/2025 F2 (SWAN) from Spain on 2025 April 21.19. His image shows a diffuse, elongated, coma with no distinct photocentre and a brighter bar of material in PA 330 degrees.
https://britastro.org/observations/observation.php?id=20250421_202852_3fb2d1e648d24ca4
The ephemeris position is at the head of the bright bar so this consists of dust that has flowed tailward from the disrupted nucleus.
The comet’s orbit implies that this is a dynamically old object so it has previously survived perihelion. It wasn’t so lucky this time.
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